1. Field of the Invention
The invention relates to the volume machining of workpieces, and more particularly to drilling, tapping, boring, milling and other operations to be performed on a sizable number of workpieces which may all be alike or may vary from each other. The invention is also particularly concerned with machining operations requiring multiple spindle tool heads, especially those in which a large number of spindles are needed.
2. Description of the Prior Art
Machine tools have been developed for mass production, including dial, shuttle, automatic multi-spindle bar and transfer machines. Low production machine tools in which high accuracy is required include single-spindle numerical machining centers, in some cases equipped with automatic tool changers to achieve higher productivity. In many cases, single-spindle machining centers will not produce the required output without using a plurality of machines, each of which has a base, motor, spindle and other components. The purchase of multiple machines thus increases the required investment to a level where other methods, such as transfer machines, become more economical. Such machines, however, may have a production capacity far in excess of that required.
A search of the subject matter of this invention revealed U.S. Pat. Nos. 3,762,036, 3,650,018, 3,810,299 and 3,789,473. The first-mentioned patent, although perhaps the most pertinent, has several drawbacks as compared with the present invention, such as inability to handle large multiple spindle heads, and inherent problems with respect to tool location accuracy.